// applyLayer is the entry-point for docker-applylayer on re-exec. This is not
// used on Windows as it does not support chroot, hence no point sandboxing
// through chroot and rexec.
func applyLayer() {
var (
tmpDir string
err error
options *archive.TarOptions
)
runtime.LockOSThread()
flag.Parse()
inUserns := rsystem.RunningInUserNS()
if err := chroot(flag.Arg(0)); err != nil {
fatal(err)
}
// We need to be able to set any perms
oldmask, err := system.Umask(0)
defer system.Umask(oldmask)
if err != nil {
fatal(err)
}
if err := json.Unmarshal([]byte(os.Getenv("OPT")), &options); err != nil {
fatal(err)
}
if inUserns {
options.InUserNS = true
}
if tmpDir, err = ioutil.TempDir("/", "temp-docker-extract"); err != nil {
fatal(err)
}
os.Setenv("TMPDIR", tmpDir)
size, err := archive.UnpackLayer("/", os.Stdin, options)
os.RemoveAll(tmpDir)
if err != nil {
fatal(err)
}
encoder := json.NewEncoder(os.Stdout)
if err := encoder.Encode(applyLayerResponse{size}); err != nil {
fatal(fmt.Errorf("unable to encode layerSize JSON: %s", err))
}
if _, err := flush(os.Stdin); err != nil {
fatal(err)
}
os.Exit(0)
}
// applyLayerHandler parses a diff in the standard layer format from `layer`, and
// applies it to the directory `dest`. Returns the size in bytes of the
// contents of the layer.
func applyLayerHandler(dest string, layer io.Reader, options *archive.TarOptions, decompress bool) (size int64, err error) {
dest = filepath.Clean(dest)
if decompress {
decompressed, err := archive.DecompressStream(layer)
if err != nil {
return 0, err
}
defer decompressed.Close()
layer = decompressed
}
if options == nil {
options = &archive.TarOptions{}
if rsystem.RunningInUserNS() {
options.InUserNS = true
}
}
if options.ExcludePatterns == nil {
options.ExcludePatterns = []string{}
}
data, err := json.Marshal(options)
if err != nil {
return 0, fmt.Errorf("ApplyLayer json encode: %v", err)
}
cmd := reexec.Command("docker-applyLayer", dest)
cmd.Stdin = layer
cmd.Env = append(cmd.Env, fmt.Sprintf("OPT=%s", data))
outBuf, errBuf := new(bytes.Buffer), new(bytes.Buffer)
cmd.Stdout, cmd.Stderr = outBuf, errBuf
if err = cmd.Run(); err != nil {
return 0, fmt.Errorf("ApplyLayer %s stdout: %s stderr: %s", err, outBuf, errBuf)
}
// Stdout should be a valid JSON struct representing an applyLayerResponse.
response := applyLayerResponse{}
decoder := json.NewDecoder(outBuf)
if err = decoder.Decode(&response); err != nil {
return 0, fmt.Errorf("unable to decode ApplyLayer JSON response: %s", err)
}
return response.LayerSize, nil
}